Effect of Complexing with Silica Nanoparticles on the Phototoxicty of Some Photosensitisers

The paper reports the results of the studies carried out by us on the changes in the phototoxicity of some hydrophilic (Chlorin-p6, Merocyanine 540, Rose Bengal) and hydrophobic photosensitisers (Curcumin) in presence of silica nanoparticles (NP). The electrostatically bound complexes of these hydrophilic photosensitisers obtained by simple mixing of PS and NP exhibited enhanced toxicity compared to the free PS. While for Chlorin-p6, the increased photostability of the Cp6-NP complex was found to be the main contributor for the enhanced toxicity, in case of Rose Bengal, the cellular uptake of the complex was larger as compared to free drug and in Merocyanine 540 a reduction in the photoisomerization rate was the main factor responsible for increased phototoxicity. Further, whereas, the covalently bound complexes of NP with Rose Bengal and Chlorin-p6 showed higher cellular uptake, these tended to aggregate over a period of time. Addition of NP to a solution of Curcumin was observed to reduce the hydrolysis of Curcumin and compared to free Curcumin, the NP-Curcumin complex was observed to result in higher uptake and phototoxicity in oral carcinoma cells and tumor spheroids.